The use of embolic devices to prevent rupture, or to minimize blood loss in case of rupture, of aneurysms has become a relatively routine medical procedure. The basic approach is to deliver the device to the site of an aneurysm using a steerable catheter that is inserted in a vessel at a remote location and is then directed to a position adjacent to the aneurysm. A pusher wire, with the embolic device attached to its distal end, is then threaded through the catheter and beyond until the device is situated in the aneurysm. The presently preferred embolic device is a coil of wire, typically platinum/tungsten alloy, that when stretched assumes a linear helical configuration and when relaxed assumes a convoluted configuration that will fill the interior of the aneurysm. The convoluted configuration may be completely random or it may be controlled using shape-memory alloys. The wire generally has a diameter of 2-6 mils while the coils are usually in the range of 10-30 mils in diameter. The coils may be of any length appropriate for the intended use. Depending on its size, from one to a great many coils may used to fill a single aneurysm. Once in place, the embolic devise initiates formation of a thrombus that is soon complemented by a collagenous material that further lessens the potential for rupture or for significant blood loss should the aneurysm break.
Once a coil is in place in the aneurysm, it is detached from the distal end of the pusher wire. Detachment can be accomplished in numerous ways including mechanically (unscrew, remove key from slot, separate ball and socket, etc.), electrolytically (disintegration of junction between metals having different standard electrode potentials) and energetically (vibrational cohesive disruption). Electrolytic detachment is one of the currently favored method of releasing an embolic device due it lack of a need for complex remote manipulation of the connection and, therefore, its speed and precision.
In virtually all electrolytically separable embolic device delivery systems presently in use, the embolic device is attached essentially to the end of the pusher wire, the difference in electrode potential between the pusher wire metal and that of which the embolic device is constructed supplying the requisite potential. The pusher wire, however, is generally relatively stiff, a necessary characteristic that allows it to be controllably threaded through the catheter and beyond to position the embolic device at the target site.
While the current devices work well, certain advantages might accrue if the distal end of the device were somewhat more flexible than the pusher wire itself. For instance, without limitation, some operators might find that such a device provides a softer feel as the embolic device is positioned and released. This invention provides such a flexible device.